1. Field of the Invention
The present invention relates to a method for removing the photoresist layer on wafer edge, and more particularly to a method for removing the photoresist layer on wafer edge and leaving the edge of the remained photoresist layer a bevel profile.
2. Description of the Related Art
It is well known that photoresist layers are widely used in modern integrated circuit processing. The photoresist layers are repeatedly applied to a semiconductor wafer by flowing a coating liquid onto the wafer while spinning the wafer, which is the spin coating or spin on process. After the spin on process, usually excess spun on photoresist material covers not only the wafer edge, but also the backside of the wafer. As shown in FIG. 1A, a spin on coated photoresist layer 12 covers the edge and backside of a wafer 10. In the following developing process, the photoresist material on the wafer edge and the backside of the wafer are very likely remained, and with the residual photoresist material are the potential contamination sources leading to various troublesome processing problems.
Conventionally, a wafer edge exposure (WEE) method and a edge bead rinse (EBR) method are used to solve the problems mentioned above. Unfortunately, the WEE method and the EBR method have some native problems individually. The WEE method utilizes additional exposing and developing processes to remove the photoresist material on the wafer edge. As shown in FIG. 1B, the photoresist material on the edge of wafer 10 is removed, and a perpendicular profile of both the edges of the photoresist layer 12 and the film covered by the photoresist layer 12 are formed. The perpendicular profile may cause peeling or breaking problems of the sequentially deposited metal or polysilicon layers. Furthermore, in the following etching process, a rough surface 14 of the wafer edge is very likely formed, and pits of the rough surface may adsorb or retain residual photoresist material. The residual photoresist material may contaminate the following processing and induce peeling or adhesion problems of the sequentially deposited films.
The EBR method uses a stream of solvent directed at the wafer edge to remove the photoresist material on the wafer edge. Because the nature of the stream of solvent, the EBR method also causes some processing problems. As shown in FIG. 1C, a residual photoresist material 16 remains after performing the EBR method. The residual photoresist material 16 may cause following deposited film adhesion and contamination problems. FIG. 1D, which is a top view of the wafer 10 having the photoresist layer 12 thereon, shows another problem of the EBR method, which is an asymmetric profile.
According to the problems of the conventional methods set forth, it is very necessary to provide a total solution. It is towards those goals that the present invention is specifically directed.
It is therefore an object of the invention to provide a method for removing the photoresist layer on the wafer edge and leaving the edge of the photoresist layer with a bevel profile, meanwhile, protecting the wafer edge from being etched.
It is another object of this invention to provide a method for removing the photoresist layer on the wafer edge without the residual and contamination problems of the photoresist material.
It is a further object of this invention to prevent the peeling and adhesion problems of following deposited films resulting from the residual and contamination problems of the photoresist material induced in the photolithography process.
To achieve these objects, and in accordance with the purpose of the invention, the invention uses a light source located under a spin on coated wafer mounted on a supporting mean of a rotatable chuck to expose the photoresist material on the wafer edge. First of all, the spin on coated wafer is mounted on the supporting mean of the rotatable chuck. Then the rotatable chuck is exposed to the light source and the wafer is rotated. Finally, the wafer is developed.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.